From e3b6c052b6a0569aa8f89c50db1ac376c42e41e0 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Wed, 29 Jan 2020 17:16:12 -0500 Subject: [PATCH] c++: Drop alignas restriction for stack variables. Since expand_stack_vars and such know how to deal with variables aligned beyond MAX_SUPPORTED_STACK_ALIGNMENT, we shouldn't reject alignas of large alignments. And if we don't do that, there's no point in having check_cxx_fundamental_alignment_constraints at all, since check_user_alignment already enforces MAX_OFILE_ALIGNMENT. PR c++/89357 * c-attribs.c (check_cxx_fundamental_alignment_constraints): Remove. --- gcc/c-family/ChangeLog | 5 +++ gcc/c-family/c-attribs.c | 62 +------------------------- gcc/testsuite/g++.dg/cpp0x/alignas17.C | 14 ++++++ 3 files changed, 20 insertions(+), 61 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/alignas17.C diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog index 023e49ae508..b15630df41b 100644 --- a/gcc/c-family/ChangeLog +++ b/gcc/c-family/ChangeLog @@ -1,3 +1,8 @@ +2020-01-29 Jason Merrill + + PR c++/89357 + * c-attribs.c (check_cxx_fundamental_alignment_constraints): Remove. + 2020-01-23 Jason Merrill * c-warn.c (conversion_warning): Change -Wsign-conversion handling. diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c index dc9579c5c60..7ec6fc848ac 100644 --- a/gcc/c-family/c-attribs.c +++ b/gcc/c-family/c-attribs.c @@ -1957,65 +1957,6 @@ fail: return res; } -/* If in c++-11, check if the c++-11 alignment constraint with respect - to fundamental alignment (in [dcl.align]) are satisfied. If not in - c++-11 mode, does nothing. - - [dcl.align]2/ says: - - [* if the constant expression evaluates to a fundamental alignment, - the alignment requirement of the declared entity shall be the - specified fundamental alignment. - - * if the constant expression evaluates to an extended alignment - and the implementation supports that alignment in the context - of the declaration, the alignment of the declared entity shall - be that alignment - - * if the constant expression evaluates to an extended alignment - and the implementation does not support that alignment in the - context of the declaration, the program is ill-formed]. */ - -static bool -check_cxx_fundamental_alignment_constraints (tree node, - unsigned align_log, - int flags) -{ - bool alignment_too_large_p = false; - unsigned requested_alignment = (1U << align_log) * BITS_PER_UNIT; - unsigned max_align = 0; - - if ((!(flags & ATTR_FLAG_CXX11) && !warn_cxx_compat) - || (node == NULL_TREE || node == error_mark_node)) - return true; - - if (cxx_fundamental_alignment_p (requested_alignment)) - return true; - - if (VAR_P (node)) - { - if (TREE_STATIC (node) || DECL_EXTERNAL (node)) - /* For file scope variables and static members, the target supports - alignments that are at most MAX_OFILE_ALIGNMENT. */ - max_align = MAX_OFILE_ALIGNMENT; - else - /* For stack variables, the target supports at most - MAX_STACK_ALIGNMENT. */ - max_align = MAX_STACK_ALIGNMENT; - if (requested_alignment > max_align) - alignment_too_large_p = true; - } - /* Let's be liberal for types and fields; don't limit their alignment any - more than check_user_alignment already did. */ - - if (alignment_too_large_p) - pedwarn (input_location, OPT_Wattributes, - "requested alignment %d is larger than %d", - requested_alignment / BITS_PER_UNIT, max_align / BITS_PER_UNIT); - - return !alignment_too_large_p; -} - /* Common codes shared by handle_warn_if_not_aligned_attribute and handle_aligned_attribute. */ @@ -2059,8 +2000,7 @@ common_handle_aligned_attribute (tree *node, tree name, tree args, int flags, /* Log2 of specified alignment. */ int pow2align = check_user_alignment (align_expr, objfile, /* warn_zero = */ true); - if (pow2align == -1 - || !check_cxx_fundamental_alignment_constraints (*node, pow2align, flags)) + if (pow2align == -1) { *no_add_attrs = true; return NULL_TREE; diff --git a/gcc/testsuite/g++.dg/cpp0x/alignas17.C b/gcc/testsuite/g++.dg/cpp0x/alignas17.C new file mode 100644 index 00000000000..b736083affc --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/alignas17.C @@ -0,0 +1,14 @@ +// PR c++/89357 +// { dg-do compile { target c++11 } } + +void g(int &); + +void f0() { + __attribute__((aligned(128))) static int x; + g(x); +} + +void f1() { + alignas(128) int x; + g(x); +} -- 2.30.2